EP 1 797 283 B1 has disclosed a generic charger device with a variable turbine geometry having guide vanes which are mounted rotatably in a vane bearing ring, wherein said guide vanes have a surface which runs in convex fashion from a profile nose to a profile end.
DE 10 2009 006 209 A1 has disclosed a further charger device with a variable turbine geometry, in particular an exhaust-gas turbocharger for a motor vehicle. By means of a correspondingly undulating form of the guide vanes in the manner of a dovetail-shaped silhouette, it is possible for an admission of a gas into multiple in flow ducts that are delimited by in each case two adjacent guide vanes to be made more uniform and oriented such that an inflow direction in the inflow duct corresponds to a flow direction of the gas in a circumferential direction. In this way, it is sought to achieve, in particular, reduced wear of the adjustment apparatus and thereby a lengthened service life of the charger device.
In general, known exhaust-gas turbochargers, or charger devices in general, are equipped with an electrical or pneumatic setting element which effects an adjustment of a variable turbine geometry. Here, the setting element is driven by way of an engine controller and moves a regulating rod which, in turn, acts on and rotates an actuator lever. The rotation of the actuator lever is transmitted by the adjustment shaft to the adjustment device. In order that the kinematic arrangement between setting device, setting element and variable turbine geometry functions smoothly, all of the components involved must exhibit a minimum amount of play, and must furthermore be freely movable.
For the adjustment or regulation of the mass flow, the profile of a guide vane included in the variable turbine geometry plays a crucial role. The aerodynamic force that acts on the guide vane profile owing to the flow passing around it generates an opening or a closing characteristic in conjunction with a bearing (in the region of a guide vane shaft). Here, an opening characteristic is advantageous because, in the event of a failure of the setting device, the guide vanes open and the vehicle can drive to a workshop without problems, albeit with reduced power. By contrast, in the case of a closing characteristic, the mass flow is reduced to such an extent that the engine is throttled with such intensity that severe malfunctions can arise. Aside from the regulating characteristic, the further demand on the profile is that it exhibits the best possible efficiency. Efficiency is a highly important feature in particular in the closed vane position, because here, the response behaviour (dynamics) of the engine is influenced. A high level of efficiency in a closed vane position corresponds to good dynamics.